Colorimetric determination of copper ion based on the silver-coated gold nanobipyramids

In this work, the sensitive colorimetric detection of Cu2+ was realized based on the redox reaction of the outer silver shell of silver coated gold nanobipyramids (Au@Ag nanoparticles) and Cu2+. The decrease of the silver nanoshell thickness leads to the tremendous blue shift of the longitudinal localized surface plasmon resonance (LSPR) peak and accompanies a vivid color change from yellow to cyan which could be employed to quanti-tatively detect the concentrations of Cu2+. This nanoprobe displays a linear range of 0.5-100 mu M with a limit of detection (LOD) of 0.16 mu M and has the most obvious color change with the lowest LOD of 12 mu M by naked eyes. In this case, the Au@Ag nanoparticles (Au@Ag NPs) are gradually etched from the nanorods to nanorices because the silver shell of Au@Ag NPs is etched by the Cu2+. In the process of anti-interference and actual water detection, it can be seen that the prepared detection sensor has specific selectivity for Cu2+, and has a certain application value in the detection of Cu2+ content in food.